BCH 461 - Test 3 - Multiple Choice
RecA protein
Catalyzes strand invasion and branch migration during recombination
DNA ligase
Seals nicks in DNA, using ATP
helicase
Unwinds DNA double helix, using ATP hydrolysis
DNA polymerase III
5'→3' DNA polymerase activity 3'→5' DNA exonuclease activity
DNA polymerase I
5'→3' DNA polymerase activity 5'→3' DNA exonuclease activity 3'→5' DNA exonuclease activity
DnaA protein
Binds to sequences in the origin of replication, unwinding the DNA, and allowing the helicase to be loaded
Type 1 topoisomerase
Changes linking number of DNA ±1, by breaking 1 strand, passing the other through, and resealing nick.
Type 2 topoisomerase
Changes linking number of DNA ±2, by making double-stranded break, passing another DNA double helix through gap, and resealing break.
Which of the following interactions/forces destabilizes the DNA double helix?
Charge-charge (electrostatic) interactions
SSB (ssDNA-binding protein)
Coats and protects single-stranded DNA during replication
β subunit (sliding clamp)
Increases processivity of DNA pol III
You start with a circular plasmid of 1000 bp. Calculate Lk0 (linking number when fully relaxed). It starts out fully relaxed, but then bacterial gyrase acts on it 6 times, and then a type I topoisomerase acts on it 3 times. What would the new linking number be? Chose both the correct Lk0 and new Lk.
Lk0 = 100, new Lk = 91
primase
Synthesizes RNA primer during DNA replication
Which of the following is not true of histones?
The display high sequence specificity when they bind to DNA.
How does the mismatch repair system "know" which strand is the newly synthesized one?
The old strand will be methylated, while the new strand will transiently be unmethylated.
Which of the following is not true of DNA general recombination?
The process involves use of a restriction endonuclease.
Restriction endonuclease sites are usually palindromes because
restriction endonucleases are usually homodimers and each subunit binds the same sequence on opposite strands.
